14 April 2005 Extradiscal ultrasound thermal therapy (ExDUSTT): evaluation in ex vivo and in vivo spine models (Invited Paper)
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Abstract
The application of heat to intervertebral discs is being clinically investigated for the treatment of discogenic back pain. The purpose of this study was to develop and test the feasibility of small ultrasound applicators that can be endoscopically placed adjacent to the disc, and deliver heating energy into the disc without puncturing the annular wall. Prototype devices were fabricated using curvilinear transducers (2.5-3.5 mm wide x 10 mm long, 5.4 - 6.5 MHz) that produce a narrow penetrating beam extending along the length of the ultrasound element. The transducer was affixed to either a flexible or rigid delivery catheter, and enclosed within an asymmetric coupling balloon with water-cooling flow. Bench measurements demonstrated 35-60% acoustic efficiencies, high-power output capabilities, and lightly focused beam patterns. The heating characteristics of these devices were evaluated with ex vivo and in vivo experiments within lumbar and cervical spine segments from sheep models and human cadaveric spine. The applicators were positioned adjacent to the annular wall of the surgically exposed discs. Ultrasound energy was focused directly into the disc to avoid heating the vertebral bodies. Multi-point thermocouple probes were placed throughout the disc to characterize the resultant temperature distributions. These studies demonstrated that ultrasound energy from these applicators penetrated the annular wall of the disc, and produced thermal coagulative temperatures of >60-65°C as far as 10 mm into the tissue. This study also showed that lower power levels and temperatures delivered for 10 minutes can generate a cytotoxic thermal dose of t43°C >240 min penetrating 5-10 mm from the annular wall.
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Chris J. Diederich, Chris J. Diederich, Adam Kinsey, Adam Kinsey, William H. Nau, William H. Nau, Richard Shu, Richard Shu, Jeffrey C. Lotz, Jeffrey C. Lotz, } "Extradiscal ultrasound thermal therapy (ExDUSTT): evaluation in ex vivo and in vivo spine models (Invited Paper)", Proc. SPIE 5698, Thermal Treatment of Tissue: Energy Delivery and Assessment III, (14 April 2005); doi: 10.1117/12.592482; https://doi.org/10.1117/12.592482
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